A simple and versatile PSA system for heavy metal determinations

An easy to build potentiometric stripping analysis system for heavy metal determinations (Zn, Cd, Pb, Cu) is described which reaches good sensitivity and precision. Main components are an IBM compatible computer, an ADDA-conversion card and two selfmade electrodes, so it can be realized for one tenth of the price of complete commercial systems. A graphite pencil lead covered with a Hg-film is used as working electrode and a Ag/AgCl electrode as a combined reference/counter electrode. Reproducibility and calibration measurements are reported, heavy metal determinations on soil samples are compared with AAS results.     

Role of magnetic forces in electrochemical reactions at microstructures

The effect of an external magnetic field (up to 0.8 T) on the anodic dissolution of microstructures has been investigated systematically. Copper and silver wires (100 microm in diameter) were embedded in epoxy resin and dissolved potentiostatically while a magnetic field was periodically switched on and off. A special feature of the thus prepared structures is that they show a smooth transition from an inlaid disk to a recessed disk electrode. An increase or a decrease of the limiting current density in the presence of B was found depending on the orientation of the magnetic field and the hydrodynamic conditions in the cell (natural or forced convection). The magnetic forces which are responsible for this are the Lorentz force and the gradient force. We propose a model which discusses the interaction of these forces with the natural and the forced convection to explain the experimental results.     

An SFG/DFG investigation of CN− adsorption at an Au electrode in 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl) amide ionic liquid

In this paper we report an SFG/DFG investigation of the adsorption of CN^? – used as a probe molecule to study the electrochemical double-layer structure – at a polycrystalline Au electrode in 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl) amide ([BMP][TFSA]) room-temperature ionic liquid (RTIL). The adsorption of CN^? yielded single SFG and DFG bands in the range from ca. 2125 to 2135 cm^?1, exhibiting a Stark tuning of ca. 3 cm^?1 V^?1. Vibrational resonances – corresponding to modes of the RTIL coadsorbed with CN^?, were found in the range from ca. 1200 to 1500 cm^?1. The study of the double-layer structure was complemented by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements, from which the differential double-layer capacity (C_DL) was estimated.     

Investigations on the kinetics of electron transfer reactions in magnetic fields

There is a controversial debate if a magnetic field can influence the rate of electron transfer (ET) reactions. In this paper, we report kinetic measurements of the ET rate constants for the redox couples [IrCl6]2-/[IrCl6]3-, [Fe(CN)6]3-/[Fe(CN)6]4-, and [Fe(H2O)6]3+/[Fe(H2O)6]2+ in magnetic fields up to 1 T. To reduce effects arising from magnetically induced mass transport (magnetohydrodynamic effect), disk microelectrodes with a diameter of 50 microm were used in potentiodynamic (cyclic and linear sweep voltammetry) and in electrochemical impedance spectroscopy experiments. None of the investigated redox couples showed a magnetic field effect on the ET rate constant.     

A simple and versatile PSA system for heavy metal determinations

An easy to build potentiometric stripping analysis system for heavy metal determinations (Zn, Cd, Pb, Cu) is described which reaches good sensitivity and precision. Main components are an IBM compatible computer, an ADDA-conversion card and two selfmade electrodes, so it can be realized for one tenth of the price of complete commercial systems. A graphite pencil lead covered with a Hg-film is used as working electrode and a Ag/AgCl electrode as a combined reference/counter electrode. Reproducibility and calibration measurements are reported, heavy metal determinations on soil samples are compared with AAS results.     

Investigations on the electrochemical preparation of gold–nanoparticle composites

The role of electrical charges in the double layers of the electrode and in particles during the electrochemical preparation of dispersion coatings was studied for the systems Au/diamond and Au/Al₂O₃. The surface charge of the electrode under the conditions of electroplating will depend on the potential of zero charge (p.z.c.). For the nanoscaled particles the sign of the surface charge was estimated from the zeta potential in dilute solutions. Successful inclusion of Al₂O₃ and diamond nanoparticles was observed when the particles and the electrode were oppositely charged. The Vickers hardness of the layers was increased by the codeposition of Al₂O₃, whereas it decreased in the case of nanodiamond.Presented at the 3rd International Symposium on Electrochemical Processing of Tailored Materials held at the 53rd Annual Meeting of the International Society of Electrochemistry, 15–20 September 2002, Düsseldorf, Germany     

Acoustic second harmonic generation from rough surfaces under shear excitation in liquids

Emission of compressional acoustic waves at the second harmonic frequency (second harmonic generation, SHG) is possible from rough surfaces undergoing oscillatory shear in liquids. This nonlinear response is a consequence of the inertial term in the Navier-Stokes equation. On a corrugated surface, the streamlines of the sheared liquid are not strictly parallel to the surface, leading to variation of pressure along the streamlines and a concomitant Bernoulli pressure. Being quadratic in speed, the Bernoulli pressure contains a static term and a term at the second harmonic frequency, 2omega. Pressure fluctuations at 2omega generate compressional waves.